The present invention relates to the control cable art and, in particular, to a method and apparatus for applying a predetermined proof loading to a cable and measuring the resultant cable length.
Numerous applications exist in which a control cable is used to control the position of moveable structure. One such application is in the aircraft art wherein aircraft wire cable assemblies are used to actuate control surfaces such as rudders and flaps. These cables must be proof loaded (pre-stretched) and the length measured before installation in the aircraft. The process for proof loading must comply with detailed specifications. For example, the specifications will detail the rate at which a specific proof load should be applied and the duration at maximum loading.
Prior to the present invention, the common method for proof loading a cable has been to apply a tension load to the cable with a hydraulic cylinder or electric power lead screw. An operator monitors the rate at which proof loading is applied and the total duration of the maximum proof load with a wrist watch. The tension force is measured with an analog force gauge and the overall length of the cable is measured at a separate location with a measuring tape.
This present method of proof loading and length measuring is time consuming, tedious and subject to human error. Also, the present method does not afford the means for collecting cable history data other than via human observation.
There is a long felt need in this art, therefore, for a reliable method and apparatus for applying a predetermined proof load to a cable and measuring the resultant cable length.